1. Field of the Invention
The present invention relates to an IC socket, particularly to an IC socket which is used by an autohandler and incorporates therein contacts corresponding to each pin of the IC serving as a device to be measured.
2. Prior Art
A conventional IC socket 12 has, for example, a construction shown in FIG. 5.
In FIG. 5, the IC socket 12 is mounted on a socket board 9, and it incorporates therein contacts 7 and 8 each corresponding to each pin of an IC 6. The contacts 7 and 8 are respectively provided with contact portions 7A and 8A, curved portions 7D and 8D and leg portions 7E and 8E as shown in FIG. 6. Leads 6A each connected to each pin of the IC 6 contact the contact portions 7A and 8A when the IC 6 is measured.
To bring the contact portions 7A and 8A and the leads 6A into surely contact with one another when the IC 6 is measured, the curved portions 7D and 8D are curved to have elasticity.
Further, the leg portions 7E and 8E are respectively inserted into through holes 9A and 9B defined in the socket board 9 (FIG. 6) and the leg portions and the through holes are connected with one another by soldering, and the leg portions 7E and 8E are also connected to an IC tester (not shown) by a cable (not shown).
The contacts 7 and 8 are respectively made of a thin metal sheet having a thickness of e.g., about 0.3 mm to correspond the IC 6 having leads 6A of small pitches.
The operation of the IC socket 12 into which the contacts 7 and 8 are incorporated when measuring the IC 6 will be now described with reference to FIG. 7.
That is, the IC 6 is first transferred on the contacts 7 and 8 by a transfer mechanism (not shown), then the leads 6A of the IC 6 are placed on the contact portions 7A of the contacts 7 and the contact portions 8A of the contacts 8 (FIG. 7(A)), thereafter the leads 6A are pressed against the contact portions 7A and 8A by a contact presser 1, thereby surely bringing the leads 6A into contact with the contact portions 7A and 8A (FIG. 7(B)).
At this time, the contacts 7 and 8 are presser by the contact pressure 1 so that the curved portions 7B of the contacts 7 and the curved portions 8B of the contacts 8 are bent within the elasticity thereof as shown in FIG. 7(B).
In the conventional IC socket 12, the contacts 7 and 8 have the curved portions 7D and 8D as set forth above. Accordingly, the distance between the contact portions 7A and 8A which are portions contacting the leads 6A of the IC 6 and the socket board 9 are long (FIG. (7)).
Further, since the contacts 7 and 8 are alternately arranged and the intervals of the contacts 7 and 8 are small so as to correspond to the leads 6A having small pitches. That is, the contacts 7 and 8 are large in conductive distance but small in areas. Accordingly, the inductance of the contacts 7 and 8 is large.
Still further, since the interval between the contacts 7 and 8 is small, the through holes 9A and 9B are formed in a staggered shape (FIG. (6)) and the positions of the legs 7E and 8E of the contacts 7 and 8 correspond to the through holes 9A and 9B (FIG. (6)).
Accordingly, the distance between the contact portions 7A and the socket board 9 and that between the contact portions 8A and socket board 9 are different from each other, thereby differentiating the impedance thereof.
Further, there are many connecting points between the IC socket 12 and a measuring circuit board (not shown), and the IC 6 is measured through the IC socket 12, the socket board 9, a cable (not shown) and the measuring circuit board so that the impedance matching is low.
In these cases, in the conventional IC to which a signal having a frequency ranging from 50 to 60 MHz is applied, there is little influence on.
However there are such drawbacks in the conventional IC socket that in an IC to which a signal having a frequency ranging from 100 MHz or more is applied, a noise voltage is generated owing to a noise current which flows to a power supply, which is caused by large inductance of the contacts 7 and 8, or caused by the low impedance matching, thereby inferiority influencing upon the measurement to reduce measuring accuracy.
That is, the contacts corresponding to a power supply pin and a ground pin of the IC 6 are respectively spaced largely from one another with, and the areas thereof are small so that inductance thereof becomes large, thereby generating a noise voltage to inferiority influence upon the measurement.
Further, the distances between the contacts 7 and 8 corresponding to each pin of the IC 6 and the socket board 9 are different from each other, and there are many connecting points between the IC socket 12 and a measuring circuit board so that the impedance matching becomes insufficient, thereby inferiority influencing upon the measurement.